POS0227 MUSSEL ADHESIVE PROTEIN-BASED ADHESIVE TO RETAIN STEM CELLS FOR CARTILAGE REGENERATION
Authors: J. Y. Ko, H. J. Cha, G. I. Im
Journal: Annals of the Rheumatic Diseases (2022)

Background Cartilage has limited intrinsic healing capacity, motivating the application of stem cells for regenerative therapies. Therapies to treat osteochondral defects using stem cell therapy-based tissue engineering have been developed and used for more than 20 years; however, the low viability and high possibility of dispersion of injected cells to target defect sites have remained challenge. Mussel adhesive protein (MAP) receiving increasing attraction as functional biomedical materials on tissue and biomedical engineering field. Because of functional underwater adhesive ability if the bioengineered MAP, therefore it could be applied on various environment of lesion site. Objectives We developed biocompatible adhesive which enables implanted chondrogenic-enhanced hASCs being strongly fixed to the lesion site of defected cartilage, and thus, the implanted cells can survive lengthily in defect site allowing cells to differentiate directly to chondrocytes. Methods MAP was produced and purified for in vivo applications using a bacterial expression system as previously reported [1]. The cell encapsulated coacervate was formulated with two polyelectrolyte, the MAP and 723 kDa hyaluronic acid (HA). The DiD labeled cell was dispensed into the solution in which the MAP solution and the HA solution were mixed in a ratio of 7:3 (v/v). MAP formed liquid microdroplets with hyaluronic acid and subsequently gelated into microparticles, which is highly viscous and strongly adhesive. In vivo efficacy of MAP in rats - the osteochondral defects were created on the patellar groove of distal femora in rats with sharp excision. After transplantation of human adipose derived stem cells (hASCs), the fluorescents image was taken in every 7 days. Animals were allocated into two groups as follows: MAP with hASCs; fibrin with hASCs. The MAP with chondro-induced hASCs were implanted on the osteochondral defect created in the patellar groove/condyle of OA-induced rabbits. Rabbits were allocated to three different groups as follows: Group 1 - Fibrin only; Group 2 - Fibrin with hASCs (1.5 x 10 6 chondro-induced hASCs); Group3; MAP with hASCs. After 12 weeks of implantation, rabbits were sacrificed for analysis. Results The fluorescence cell images exhibit the viability of cells under encapsulated condition in coacervate. The cell viabilities were determined with Live/Dead fluorescent staining. The implanted cells were labeled with DiD for in vivo visualization. After 35 days, fluorescent signals were more potently detected for MAP with hASCs group than Fibrin with hASCs group in osteochondral defect model. Implanted hASCs had been remained in target defect rather than diffused to other sites of the knee. Moreover, histological assessment showed that MAP with hASCs group had the best healing and covered with hyaline cartilage-like tissue. The staining image shows that MAP with hASCs group were filled with perfectly differentiated chondrocytes. Although Fibrin with hASCs group had better healing than fibrin only group, it was filled with fibrous cartilage which owes its flexibility and toughness. As MAP with hASCs group has higher possibility of differentiating to complete cartilage, Fibrin only group and Fibrin with hASCs group have failed to treat OA by rehabilitating cartilage. In order to clarify the evidence of remaining human cell proving efficacy of newly developed bioadhesive, human nuclear staining was proceeded with sectioned rabbit cartilage tissue. The results explicitly showed MAP with hASCs group have retained more human cells than Fibrin only and Fibrin with hASCs groups. Conclusion We investigated the waterproof bioadhesive supporting transplanted cells to attach to defect lengthily in harsh environment, which prevents cells from leaked to other region of cartilage. Collectively, the newly developed bio-adhesive, MAP, could be successfully applied in OA treatment as a waterproof bioadhesive with the capability of the strong adhesion to target defect sites. Our study suggests a new effective strategy for cartilage regeneration using MAP in tissue engineering fields References [1]Biomaterials (2007) 3560-3568 Acknowledgements This research was supported by a grant of the Korea Health Technology R&amp;D Project through the Korea Health &amp; Welfare, Republic of Korea (grant number: HI20C0090) and the National Research Foundation of Korea (NRF-2020R1A2C2008266 and 2019R1I1A1A01043778). Disclosure of Interests None declared